FIG. 1 shows schematically a block diagram of a CT scanning system; the block diagram is only showed by way of example, and persons skilled in the art can appreciate that, an actual CT scanning system may have more or less or different components as compared with the system shown in FIG. 1 according to different system configurations. It can be seen from FIG. 1 that, a CT scanning system is generally comprised of four subsystems: an operation console (OC), a gantry, a scanning table and a power distribution unit (PDU), wherein the gantry subsystem further comprises such components as a data-detection-acquisition part and an X-ray generator.
The operating overview of the CT scanning system will be described in connection with FIG. 1. The OC controls the entire system, according to the operator's operations. The OC sends instructions to the Table gantry Processor (TGP) board (the TGP board is a main controller of the scanning table/gantry subsystems) on the stationary part of the gantry, and the TGP board subsequently controls the gantry and the Scanning table according to some of these instructions. The TGP board passes some instructions of the OC to the On gantry Processor (OGP) board mounted on the rotational part of the gantry. According to the destinations of these instructions passed from the TGP board, the OGP board passes these instructions to such components as the Data Acquisition System (DAS), X-ray Generator, etc., respectively, such that the OC can control these components. The OC can also send an instruction whose destination is the OGP board, and this instruction is performed by the OGP board per se. Reversely, the OC receives status information from the TGP board or from other components (such as the OGP board) via the TGP board.
As shown in FIG. 1, the gantry can be divided into the stationary part and the rotational part, and the communication between the stationary part and the rotational part is realized by a slip ring; the slip ring is a rotational mechanism allowing exchange of power and signal, and the link on the slip ring for transmitting raw data is different from the link on the slip ring for communication between the OGP board and the OC (via the TGP board). The stationary part of the gantry is mainly controlled by the TGP board, and the TGP board is in communication with the OGP board via cables and the slip ring.
FIG. 2 is a block diagram of the X-ray tube and the data detection-acquisition part; FIG. 3 is schematic diagram of the X-ray tube and the data detection-acquisition part. The data detection-acquisition part consists of the DAS and a detector that are located on the rotational part of the gantry. X-ray data acquired by the detector is converted to light, then to electrical signals in the detector and then sent to the DAS. The DAS digitizes, serializes and performs offset correction on the signal and then sends it via the slip ring to the Operator Console for image reconstruction. In addition, persons skilled in the art understand that the detector can also be comprised in the DAS.
Specifically, the DAS can comprise CAM board, DDP board and CIF board, as shown in FIG. 4. The CIF board exchanges signals with the OGP board to control and synchronize the data acquisition, and generates control and timing signals to the other boards in the DAS. The CAM board converts electrical current that is generated by the detector and is proportional to the X-ray intensity to voltage signal. In the CAM board, the voltage signal is amplified to an appropriate level, converted to serial digital data, and then converted to parallel data. The offset correction of the data is performed in the DDP board. The data is then sent to a transmission preparation module. As known by persons skilled in the art, the transmission preparation module and the DAS are separate components in traditional CT scanning systems, and the existing CT scanning systems do not have a separated transmission preparation module, and integrate the functions of the transmission preparation module into the DAS instead. The CT scanning system of some embodiments of the present invention also integrate the functions of the transmission preparation module into the DAS without a separated transmission preparation module; the separation of the transmission preparation module from the DAS as shown in the drawings is only used to more conveniently explain the functions of the DAS.
The transmission preparation module performs the following preparation tasks of data transmission: FEC error correction code generation, parallel/serial conversion, view packing, and electric to light signal conversion. In the transmission preparation module, the FEC encoder adds error correction code to conduct error detection and error correction to the transmitted data in the OC; the optical transmitter converts the electric signal to light signal, which is sent to the RF transmitter by optical fiber. The RF transmitter transmits the signal to the RF receiver on the stationary part side of the gantry, and in the RF receiver, the signal is converted again to light signal and is transmitted by optical fiber to the DAS Interface (DASIF) in the OC. This interface converts the serial light signal raw data from the DAS into parallel electric signal raw data. The RF transmitter antenna and the RF receiver antenna are both located on the slip ring.
Data that is generated and transmitted by the DAS (including the transmission preparation module) is called raw data, so the transmitting path of raw data include the optical fiber from the DAS to the RF transmitter, the RF transmitter, the slip ring, the RF receiver, and the optical fiber from the RF receiver to the OC. If a failure occurs in any component on the transmitting path of raw data, a problem will occur in the transmission of raw data. Although the CT scanning system adds error correction codes when transmitting raw data, many data problems, such as missing data package, cannot be corrected by the error correction codes. In addition, the DAS does not store the backup of raw data in the rotational part of the gantry when transmitting raw data to the OC. This design does not provide any redundancy backup capacity for raw data, so it is very hard to avoid the following drawbacks.
When, e.g., the occasional problems of data are caused by interference sources (unexpected factors, such as voltage mutation or mobile phone signal interference near the gantry, etc.) that occasionally appear on the transmitting path of raw data or data receiving interface, and these problems cannot be corrected by error correction codes. The OC will remedy the problem of data package via the proper post-processing (e.g., interpolation scheme), but the image quality of reconstruction will be impacted by doing so. Moreover, when the number of data problems reaches a certain threshold, such that these data contain too many problems to be remedied by post-processing of image reconstruction, the OC will abort scanning. At that moment, the scanning object me be re-scanned because the data received and stored in the OC before the scanning is aborted cannot be used for image reconstruction due to containing too many problems. However, re-scanning will expose the scanning object to more radiation.
In the case of a serious failure, such as the transmitting path of raw data being damaged, soft/hardware invalidation on the OC, or power down of the OC, scanning will also be aborted. In this case, some data that is transmitted prior to the abortion of the scan, is missed due to the serious failures, such that the data received and stored in the OC before scanning is aborted is not intact, so the restoring scanning cannot be started from the point at which it is aborted, and the object being scanned must also be re-scanned.
Upon the completion of a scan, the rotational part of the gantry does not store the backup of raw data. In the on-site detection of failures in the transmitting path of raw data, the data that can be analyzed after the scan is complete is only the data containing problems that is stored in the OC, such that persons skilled in the art cannot quickly locate in which sections of the transmitting path of raw data failures appear, thereby leading to very low detection efficiency.